Due to their many advantages in power, volume, cost, and performance, flat panel displays have now almost entirely supplanted cathode ray tubes (CRTs). CRTs, however, did have one advantage that many modern displays lack. In a CRT device, after the electron beam scans the phosphor, the phosphor naturally fades to black until it is stimulated again. In contrast, the pixels of many flat panel displays maintain their bright or dark states from one frame to the next. The persistence of such flat panel displays may cause motion artifacts (e.g., tailing) to be perceived as the eye scans across the image.
Some flat panel displays mitigate such motion artifacts by black frame insertion, which requires doubling the frame rate and driving alternate frames black. Black frame insertion requires higher video bandwidth to the pixel array, with associated higher power and complexity.
Liquid crystal displays (LCDs) may adopt a similar technique by pulsing the back light, so that pixels are illuminated for a shorter period. However, non-uniformity problems may result as pixels near the top of the display are scanned earlier than those near the bottom, and so have a different phase relationship to the backlight timing.
Further mitigation may be possible with a segmented backlight synchronized to the scanning of the pixel array, but this adds complexity and in any case is impractical for certain applications (e.g., microdisplays) that are illuminated by a single LED backlight. Other displays may achieve global blanking by controlling one or more common signals to the pixel array, such as VCOM in the case of an LCD, or the anode or cathode supplies in an organic light emitting diode (OLED) display. Such techniques, however, may have uniformity issues similar to those described for backlight blanking in the preceding paragraph.
In many liquid crystal display (LCD) configurations, and particularly those employing the commonly-used twisted nematic (TN) phase, the brightness of a pixel is modulated by the voltage applied across the liquid crystal (LC) cell. The voltage affects the degree to which the LC material rotates polarized light, which in turn controls how much light passes through an exit polarizer. In other words, an LCD is a passive device that acts as a light valve. The managing and controlling of data to be displayed is typically performed by one or more circuits, which are commonly referred to as display driver circuits or simply drivers.
Grayscale can be achieved by driving varying analog voltages to LCD pixels. Analog video amplifiers are often used in the video signal path of LCD driven circuits. If the video signal source is digital, then one or more digital-to-analog converters (DACs) will typically be used to convert the digital video signal into a corresponding analog video signal.